The vulnerability identified as CVE-2025-59466 in Node.js arises from improper handling of stack overflow errors when the async_hooks API is enabled. Async_hooks is a low-level API used to track asynchronous resource lifecycles and is widely leveraged by frameworks and Application Performance Monitoring (APM) tools through AsyncLocalStorage. Normally, Node.js and the underlying V8 engine attempt to recover from stack space exhaustion by throwing a catchable error, allowing frameworks to maintain service availability. However, due to a bug, when recursion in user code exhausts the stack space with async_hooks enabled, Node.js exits immediately with exit code 7 (Internal Exception Handler Run-Time Failure) instead of throwing an error. This abrupt termination causes denial-of-service (DoS) conditions, as applications crash without graceful error handling. The vulnerability affects all Node.js versions from 8.x (the first to include async_hooks) through 18.x, many of which are end-of-life and unpatched. The Node.js project has released fixes in versions 20.20.0, 22.22.0, 24.13.0, and 25.3.0, which detect stack overflow and re-throw errors to user code rather than exiting. Despite the fix, Node.js treats this as a mitigation rather than a full resolution due to the ECMAScript specification not defining stack exhaustion behavior, V8 engine limitations, and the design of the uncaughtException handler. The vulnerability impacts numerous popular frameworks and tools, including React Server Components, Next.js, Datadog, New Relic, Dynatrace, Elastic APM, and OpenTelemetry, all of which rely on AsyncLocalStorage. Exploitation requires unsanitized input controlling recursion depth, making input validation a critical defense. The vulnerability can cause widespread service disruption and degrade developer experience by making error handling unpredictable. Node.js also released fixes for related high-severity vulnerabilities concurrently. Organizations are urged to update Node.js versions promptly and implement robust defenses against stack exhaustion to maintain service availability.

For European organizations, this vulnerability poses a significant risk of denial-of-service attacks against Node.js-based applications, which are prevalent in web services, cloud platforms, and enterprise applications. The abrupt server crashes can lead to service outages, impacting business continuity, customer experience, and operational reliability. Organizations relying on frameworks like React Server Components and Next.js, or APM tools such as Datadog and New Relic, are particularly vulnerable due to their dependence on AsyncLocalStorage and async_hooks. The disruption can affect critical services, especially in sectors like finance, e-commerce, telecommunications, and public services, where Node.js is commonly used. Additionally, the difficulty in gracefully handling stack overflow errors complicates incident response and recovery. The vulnerability also increases the attack surface for threat actors aiming to cause operational disruption without needing elevated privileges or complex exploits, as unsanitized input controlling recursion depth suffices. This can lead to reputational damage and financial losses. The widespread use of affected Node.js versions, including many unpatched end-of-life releases, exacerbates the risk. European cloud service providers hosting Node.js applications must prioritize mitigation to prevent cascading outages. Overall, the vulnerability threatens availability and operational integrity across diverse industries in Europe.

1. Immediately upgrade Node.js to patched versions 20.20.0, 22.22.0, 24.13.0, or 25.3.0 where feasible, prioritizing production environments. 2. For legacy or end-of-life Node.js versions that cannot be upgraded, consider isolating vulnerable services or migrating critical workloads to patched environments. 3. Implement strict input validation and sanitization to control recursion depth in user-supplied data, preventing exploitation via stack exhaustion. 4. Review and audit usage of async_hooks and AsyncLocalStorage in application code and dependencies to identify risky recursion patterns. 5. Enhance monitoring and alerting for abnormal process exits (exit code 7) and increased stack usage to detect potential exploitation attempts early. 6. Collaborate with framework and APM tool maintainers to apply updates and patches that address async_hooks-related vulnerabilities. 7. Employ runtime protections such as process supervisors or container orchestrators configured to automatically restart crashed Node.js processes to minimize downtime. 8. Conduct security testing focusing on recursion and stack exhaustion scenarios in asynchronous code paths. 9. Educate developers on the risks of unsanitized input controlling recursion and promote secure coding practices around async_hooks usage. 10. Maintain an incident response plan tailored to DoS conditions caused by stack overflows to ensure rapid recovery.